Development of Novel Euthanasia and Depopulation Methods for Neonatal Poultry and Caged Laying Hens
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Rapid depopulation of infected poultry is the primary US strategy to contain and eradicate reportable diseases. Two experiments were conducted to develop a compressed air foam based depopulation method for caged layer hens. The hypothesis of the first experiment was that a compressed air foam (CAF) system may be used as an alternative means to carbon dioxide (CO₂) inhalation for depopulating caged layer hens. In order to assess the stress response (corticosterone, CORT), young and spent hens were subjected to five treatments: normal handling (NEG control), CO2 added to a chamber, CO₂ pre-charged chamber, CAF in cages, and CAF in a chamber. The times to cessation of movement (COM) were determined using spent hens, which were randomly assigned to three treatments: CAF in cages, CO₂ added to a chamber, and aspirated foam. Serum CORT levels of hens subjected to foam treatments were similar to CO₂ inhalation except that of spent hens in the CAF in a chamber group. Times to COM of spent hens subjected to CAF in cages and aspirated foam were significantly longer as compared to CO₂ in a chamber treatment. These data suggest that applying CAF in cages is a viable alternative for layer hen depopulation during a reportable disease outbreak. The second experiment posited that infusion of gases such as CO₂ and nitrogen (N2) into the CAF would reduce physiological stress and shorten time to cessation of movement of spent hens. There were six treatments in this experiment: a negative control, CO₂ inhalation, N2 inhalation, CAF with air (CAF), CAF with 50% CO₂ (CAF CO₂), and CAF with 100% N₂ (CAF N₂). Serum CORT and serotonin levels as well as time to COM were measured. The addition of CO₂ in CAF significantly reduced the foam quality as compared to the addition of N₂. The addition of gases into the foam did not result in significant improvements in the CORT and serotonin levels of spent hens as compared to foam with air. The time to COM of spent hens in the CAF N₂ treatment was significantly shorter than CAF and CAF CO₂ treatments, but longer than the gas inhalation treatments. The findings suggest that the addition of N₂ into foam is advantageous in terms of shortening time to death and foam quality than infusion of CO₂ for mass depopulation of caged layers. Public concern on the use of maceration as a method of euthanasia of male layer chicks has resulted in negative publicity of the egg industry. We hypothesized that gas inhalation and low atmospheric pressure stunning (LAPS) are viable and humane alternatives for chick euthanasia. The study consisted of seven treatments: breathing air (NEG), 25% CO₂, 50% CO₂, 75% CO₂, 90% CO₂, 100% nitrogen (N₂), and LAPS. A custom made vacuum system was used to reduce air pressure inside the chamber from 101.3 kPa to 15.3 kPa for the LAPS treatment. Serum CORT and serotonin levels as well as latencies to loss of posture and motionlessness of day of hatch chicks were evaluated. The 25% and 50% CO₂ treatments were discontinued as the majority of the chicks recovered. The chicks in the NEG group had significantly higher levels of CORT but lower concentration of serotonin than the other four euthanasia treatments. The latencies to loss of posture and motionlessness of chicks exposed to 75% and 90% CO₂ were significantly shorter than the LAPS and N₂ inhalation treatments. These data suggest that LAPS and gas inhalation can be viable alternatives to maceration.
SubjectCaged laying hens
male layer chicks
compressed air foam
Gurung, Shailesh (2017). Development of Novel Euthanasia and Depopulation Methods for Neonatal Poultry and Caged Laying Hens. Master's thesis, Texas A & M University. Available electronically from